1. Field of the Invention
This invention relates to an aligner for light exposure of a master-plate circuit pattern or the like onto a circuit board in the manufacture of a print circuit board.
2. Prior Art
Recently, the photolithography technique for IC fabrication has been used in forming the conductor pattern onto the print circuit board and the like.
This technique uses a master plate depicted with a formation pattern to be exposed to projection light thereby depicting the print circuit board with the same pattern as that of the master plate.
The master plate, usually, uses a film mask. It is a usual practice to carry out exposure in a state the film mask is close contacted with or in proximity onto the print circuit board.
Prior to placing the mask and the circuit board in proximity or close contact, the both require alignment with each other. The mask or the board is moved and aligned in an XYxcex8 direction. Thereafter, the both are brought into close contact for exposure.
Meanwhile, in recent years the circuit board has been reduced in size. For the efficiency in the manufacture process, it is a practice to demarcate a large-sized board into a plurality of areas and repeat exposure to light on the area-by-area basis. Thereafter, the board is cut and used.
However, the increase of board size has raised a problem of lowered accuracy due to warp or deformation of the board. The board is usually structured to be sucked onto a suction base by a suction mechanism. However, there is a problem that air leak occurs through between the base and the board due to warp or deformation thereby decreasing vacuum and lowering the suction force. Consequently, the board cannot be kept in sufficient flatness upon exposure thus incurring lowering in exposure accuracy.
It is an object of the present invention to solve such a conventional disadvantage.
In order to achieve the object, the present invention is to provide an aligner comprising a base on which a to-be-exposed substrate is rested and a sucking unit for sucking the to-be-exposed substrate on the base, the sucking unit being capable of sucking the to-be-exposed substrate only at a part thereof. In the case that the aligner is capable of partly exposing the to-be-exposed substrate to light, the substrate can be sucked only at a part to be exposed to light. With this structure, the efficiency of suction is high as compared to the case of sucking the entire substrate, and positive suction is possible even where there is warp or the like in the board, improving exposure efficiency.
In exposure, a photomask is used which has a predetermined pattern. This photomask is arranged for contact with or proximity to the to-be-exposed substrate.
Light is radiated from a light source unit to transfer the pattern of the photomask onto the substrate. In a preferred embodiment, the photomask can be aligned to an arbitrary area of the to-be-exposed substrate so that the to-be-exposed substrate can be exposed to light a plurality of number of times while being changed in area. A sucking unit is structured to suck onto the base the to-be-exposed substrate at each area corresponding to an area for exposure. By a control unit, the to-be-exposed substrate is sucked at each of the areas onto the base and exposed to light after alignment. With this structure, because the substrate can be sucked only at the area correspondingly to an area for exposure, suction efficiency is improved. Due to this, even where there is warp or deformation in the substrate, positive suction is possible. Particularly, where the photomask is of a type to contact the substrate, the weight of the photomask enhances the closeness in contact between the substrate and the base, further improving the suction efficiency in the exposure area.
Incidentally, usually the mask and the aligner are arranged in a vertical direction wherein the mask is arranged vertically above the to-be-exposed substrate. However, the mask and the to-be-exposed substrate can be arranged standing to position the mask and the to-be-exposed substrate with a spacing in a horizontal direction.